Illumination device with semiconductor light-emitting elements

ABSTRACT

An illumination device includes a base board, an insulator, a conductor, a plurality of semiconductor light-emitting elements and a light-transmissive sealing member. The base board includes a surface and projection portions. The projection portion is formed to become gradually thicker from its end toward the surface of the base board. The insulator is formed on the surface. The conductor is formed on the insulator. The semiconductor light-emitting elements are mounted on the projection portions. The semiconductor light-emitting elements are electrically connected to the conductor via connection members. The sealing member covers the insulator, the projection portions, the semiconductor light-emitting elements and the connection members.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Applications No. 2006-324606, filed Nov. 30, 2006;No. 2006-353468, filed Dec. 27, 2006; No. 2007-075637, filed Mar. 22,2007; No. 2007-075638, filed Mar. 22, 2007; No. 2007-082882, filed Mar.27, 2007; and No. 2007-250227, filed Sep. 26, 2007, the entire contentsof all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an illumination device which uses, aslight sources, a plurality of semiconductor light-emitting elements suchas light-emitting diode chips.

2. Description of the Related Art

Jpn. Pat. Appln. KOKAI Publication No. 2002-94122 discloses anillumination device in which a plurality of light-emitting diode chipsare arranged on a base board. In this illumination device, in order toachieve enhancement of light emission efficiency, an increase in lightoutput and elongation in lifetime, heat that is produced by thelight-emitting diode chips is made to quickly escape to the base board,thereby enhancing heat radiation properties.

To be more specific, the base board is formed of a metallic materialwith excellent heat conductivity, such as aluminum. The base board has aflat mounting surface and a plurality of columnar projection portionswhich project from the mounting surface. An insulation member is stackedon the mounting surface of the base board. The insulation member hasrecesses at positions corresponding to the projection portions. Throughholes, which penetrate the insulation member, are formed at bottoms ofthe recesses. The projection portions of the base board are put in thethrough holes. A distal end face of each projection portion is locatedat the bottom of the recess. A light-emitting diode chip is bonded tothe distal end face of each projection portion. Thereby, thelight-emitting diode chip is thermally connected to the distal end faceof each projection portion.

A wiring pattern is formed on the insulation member. The wiring patternhas a plurality of terminal portions which are located at the bottoms ofthe recesses. The terminal portions of the wiring pattern and a pair ofelectrodes of the light-emitting diode chip are electrically connectedvia bonding wires.

Further, a sealing member is filled in the recesses of the insulationmember. The sealing member is formed of a light-transmissive resin. Aphosphor is mixed in the sealing member. The sealing member covers thelight-emitting diode chips, wiring pattern and boding wires, andprotects connection parts between the bonding wires and the electrodes.

In the conventional illumination device disclosed in the above-describedJapanese KOKAI Publication, the light-emitting diode chips which produceheat are thermally connected to the projection portions of the metallicbase board. Thus, the heat produced by the light-emitting diode chipscan directly be conducted to the base board, and the heat can beradiated from the base board to the outside of the illumination device.

However, in the conventional illumination device, although thetemperature rise of the light-emitting diode chip can be suppressed, theextraction of light emitted from the light-emitting diode chips is notadequate. Specifically, part of the light emitted from thelight-emitting diode chips is absorbed by the phosphor in the sealingmember, and is converted to light of some other color and radiated. Atthis time, part of the light, which is emitted toward the projectionportions of the base board, is reflected by the projection portions andis extracted to the outside of the illumination device.

In the conventional illumination device, when the light is extracted,each projection portion is located inside the through hole of theinsulation member, and thus the entire periphery of the projectionportion is surrounded by the insulation member. As a result, the lightthat is radiated from the phosphor can be reflected only by a limitedpart of the distal end face of the projection portion, which is exposedto the periphery of the light-emitting diode chip. Hence, the use of thelight from the light-emitting diode chips is not sufficient, and thebrightness may become deficient, for example, when purposes of use forgeneral illumination are assumed.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to provide an illumination devicewhich can efficiently extract light while suppressing a temperature riseof semiconductor light-emitting elements.

In order to achieve the object, an illumination device according toclaim 1 includes a base board with heat radiation properties, aninsulator, a conductor, a plurality of semiconductor light-emittingelements and a light-transmissive sealing member. The base boardincludes a surface and projection portions formed to become graduallythicker from its ends toward the surface of the base board. Theinsulator is formed on the surface of the base board. The conductor isformed on the insulator. The semiconductor light-emitting elements aremounted on the projection portions of the base board. The semiconductorlight-emitting elements are electrically connected to the conductor viaconnection members. The sealing member covers the projection portions,the semiconductor light-emitting elements, the connection members andthe conductor.

In the invention of claim 1, a metallic material or a carbon-basedmaterial is usable as the material of the base board. Preferableexamples of the metallic material are copper, aluminum and an alloythereof, which have good heat radiation properties. Examples of thecarbon-based material are carbon and graphite. In particular, in thecase where carbon-based powder material is used, the carbon-based powdermaterial may be compressed by a mold, and thereby the base board can beformed. Hence, when the projection portions are formed on the baseboard, there is no need to subject the base board to etching treatment.Therefore, the base board with the projection portions can easily beformed in a desired shape. Moreover, by choosing the carbon-basedmaterial as the material of the base board, the influence of recentsteep rise in price of copper can be eliminated, and the increase incost of the base board can advantageously be suppressed. The projectionportions can also be formed by laser processing or machining.

In the case where the base board is metallic, it is preferable to setthe thickness of that part of the base board, which is covered with theinsulator, at 0.25 mm to 0.50 mm. Thereby, the precision in thicknessdimension of the base board can be improved. In addition, when bondingwires are used as the connection members, the variance in strength ofconnection parts between the bonding wires and the conductor can be morereduced as the precision in thickness of the base board becomes higher.Therefore, the reliability of connection between the bonding wires andthe conductor can be enhanced.

A glass epoxy plate, for instance, is usable as the insulator. In orderto obtain good light reflection performance, it is preferable to use awhite glass epoxy plate. In the case where the white glass epoxy plateis used as the insulator, light emitted from the semiconductorlight-emitting elements is not absorbed by the insulator and isreflected by the insulator. Thus, advantageously, light can efficientlybe extracted.

The conductor is formed of a metallic material with good electricalconductivity, such as copper or silver. In the case where the base boardis metallic, the conductor can be formed, by etching, on that surface ofthe insulator, which is opposite to the base board. Alternatively, forexample, the conductor may be attached to the insulator via an adhesive.

Furthermore, a resist layer may be stacked on the insulator, and theconductor may be covered with the resist layer. According to thisstructure, the insulation properties and anti-migration properties ofthe conductor can be improved, and the oxidation of the conductor can beprevented.

A blue LED chip which emits blue light or an LED chip which emitsultraviolet, for instance, is usable for the semiconductorlight-emitting elements. Moreover, at least two kinds of LED chips,which are chosen from a blue LED chip, a red LED chip and a green LEDchip, may be used in combination. For example, in an illumination devicewhich obtains white emission light by using the blue LED chip as thelight source, a sealing member, in which a phosphor that is excited byblue light and mainly emit yellow light are mixed, is used. Furthermore,in the case where the LED which emits ultraviolet is used as the lightsource, it is possible to use a sealing member which contains a phosphorthat is excited by ultraviolet and mainly emit red light, a phosphorthat are excited by ultraviolet and mainly emit green light, and aphosphor that is excited by ultraviolet and mainly emit yellow light.

A bonding material, for instance, is used when the semiconductorlight-emitting element is mounted on the projection portion of the baseboard. Preferably, the thickness of the bonding material should be setat 10 μm or less within such a range as not to lose the inherentadhesion function of the bonding material. In addition, in order toefficiently extract light, it is preferable to choose a bonding materialwith light transmissivity, and to reflect part of the light, which isemitted from the semiconductor light-emitting element, by the projectionportion.

The sealing member shields the semiconductor light-emitting elementsfrom outside air and moisture, thereby preventing a decrease in lifetimeof the semiconductor light-emitting elements. Light-transmissivesynthetic resins, such as epoxy resin, silicone resin and urethaneresin, are usable for the sealing member. Further, instead of thelight-transmissive synthetic resin, a transparent low-melting-pointglass, for example, can be used for the sealing member.

According to the invention of claim 1, power is supplied to thesemiconductor light-emitting elements via the conductor and theconnection members, thereby causing the semiconductor light-emittingelements to emit light. The light radiated from the semiconductorlight-emitting elements is extracted through the sealing member to theside opposite to the base board. The insulator, which effects electricalinsulation between the conductor and the base board, is not presentbetween the projection portions of the base board and the semiconductorlight-emitting elements, and the semiconductor light-emitting elementsare mounted on the projection portions. Thus, when the semiconductorlight-emitting elements are lighted, the heat that is produced by thesemiconductor light-emitting elements is directly conducted to theprojection portions, without being shielded by the insulator.

In addition, since the cross-sectional area of the projection portiongradually increases from the end of the projection portion toward thebase board, the thermal conduction from the semiconductor light-emittingelement to the base board becomes easier. As a result, the heat of thesemiconductor light-emitting elements is efficiently conducted to thebase board and is radiated from the base board to the outside of theillumination device. Therefore, the temperature rise of thesemiconductor light-emitting elements can surely be prevented.

Furthermore, the projection portions, on which the semiconductorlight-emitting elements are mounted, penetrate the insulator. Thus, partof the light, which is radiated from the semiconductor light-emittingelements, travels towards the projection portions without being blockedby the insulator. Since each projection portion flares from the endthereof toward the surface of the base board, the light that is incidenton the projection portion can positively be reflected in thelight-extraction direction opposite to the base board. Therefore, thelight emitted from the semiconductor light-emitting elements canefficiently be extracted by making use of the projection portions thatfacilitate the heat radiation of the semiconductor light-emittingelements.

In the invention of claim 2, the outer peripheral surface of theprojection portion flares from a distal end face of the projectionportion toward the base board. The outer peripheral surface of theprojection portion may not flare continuously, but may flare stepwise.According to this structure, part of the light emitted from thesemiconductor light-emitting element can be reflected in thelight-extraction direction by making use of the inclination of the outerperipheral surface of the projection portion.

In the invention of claim 3, the insulator has a plurality of throughholes, through which the projection portions penetrate, and each of thethrough holes has a greater diameter than the projection portion.According to this structure, when the insulator is stacked on the baseboard, the projection portions penetrate the through holes. Therefore,the alignment between the base board and the insulator can easily beperformed. In addition, interference between the insulator and theprojection portions can be prevented, and the insulator does not liftfrom the surface of the base board. Therefore, the insulator can bestacked on a proper position on the surface of the base board.

In the invention of claim 4, the insulator is bonded to the surface ofthe base board via the adhesive. A part of the adhesive protrudes to theinside of the through hole. The adhesive, which is usable, may be in apaste form or in a sheet form. The adhesive is disposed on that regionof the base board, which excludes the projection portions.

According to this structure, the entire region between the base boardand the insulator can be filled with the adhesive, and no gap, which iscontinuous with the through hole, occurs between the base board and theinsulator. Therefore, when the sealing member is heated, it is possibleto prevent air, which remains in the gap, from becoming bubbles andflowing into the inside of the sealing member. In other words, it ispossible to avoid such a situation that the air in the gap becomesbubbles and stays within the sealing member.

In the invention of claim 4, the adhesive, which protrudes into thethrough hole, should preferably reach the same height as the surface ofthe insulator. Thereby, since most of the gap between the through holeand the projection portion is filled with the adhesive, air hardlyremains between the through hole and the projection portion, forexample, when the non-solidified resin material, of which the sealingmember is to be formed, is filled in the surrounding region of theprojection portion.

Moreover, bonding between the projection portion and the insulator canbe effected by the adhesive that protrudes into the through hole. As aresult, the strength of adhesion of the insulator to the base board canbe improved. Besides, since the adhesive that protrudes functions as anelectrical insulator, electrical insulation between the conductor thatis provided on the insulator and the projection portion canadvantageously be secured.

Preferably, the adhesive should be milk white, or white. Thereby, partof the light that is emitted from the semiconductor light-emittingelements can be reflected by the adhesive, which protrudes into thethrough hole, in the light-extraction direction opposite to the baseboard. Therefore, the adhesive that protrudes into the through holeeffectively contributes to more efficient extraction of light.

In the invention of claim 5, a light reflective layer is formed on thedistal end face of each projection portion, and the semiconductorlight-emitting element is bonded to the light reflective layer via alight-transmissive bonding material.

Preferably, the light reflective layer should be formed of, for example,a silver plating layer. Since the silver plating layer does not hinderheat conduction from the semiconductor light-emitting element to theprojection portion, the heat of the semiconductor light-emittingelements can efficiently be let to escape to the projection portions.Besides, the silver plating layer has a light reflectance of 90% ormore. Thus, the light, which is made incident on the silver platinglayer through the light-transmissive bonding material, can efficientlybe reflected in the light-extraction direction.

A light-transmissive synthetic resin, such as transparent siliconeresin, or frit glass is usable as the bonding material. There is verylittle possibility that the transparent silicone resin deteriorates witha change in color due to heat. Thus, with the use of the transparentsilicone resin as the bonding material, the bonding material does notshield light that is incident on the light reflective layer, or hinderextraction of light that is reflected by the light reflective layer.Therefore, extraction of light can efficiently be performed for a longtime.

In the invention of claim 6, a side light reflective layer is formed onthe outer peripheral surface of each projection portion. The side lightreflective layer is continuous with the light reflective layer, and witha part of the adhesive that protrudes into the through hole. Further,the sealing member includes a phosphor which is excited by light emittedfrom the semiconductor light-emitting elements.

It is preferable that the side light reflective layer be formed of ametallic plating layer of the same kind as the light reflective layer ofthe projection portion. Thereby, a major part of the projection portioncan be used as a light reflective surface. According to this structure,when the phosphor in the sealing member is excited, light is emittedfrom the phosphor. Part of the emitted light is incident on the sidelight reflective layer on the outer peripheral surface of the projectionportion. As a result, the light from the phosphor can efficiently bereflected in the light-extraction direction by making use of the sidelight reflective surface.

In the invention of claim 7, the dimension of protrusion of the adhesiveinto the through hole is 0.2 mm or less. With this structure, despitethe adhesive being continuous with the side light reflective layer, adecrease in area of the side light reflective layer becomes practicallyignorable. In addition, even if the adhesive is colored, for example, inbrown or black, the light absorption function of the protruding adhesivebecomes very weak and substantially ignorable. Therefore, the adhesivethat protrudes into the through hole does not adversely affect theextraction of light.

In the invention of claim 8, when the light reflectance of the insulatoris made different from the light reflectance of the adhesive, it ispreferable to make the light reflectance of the adhesive lower than thelight reflectance of the insulator. For example, in the case where theinsulator is white, it is preferable to make the adhesive brown orblack. Thereby, a sharp difference in color can be given between theinsulator and the adhesive. As a result, the position of the throughhole of the insulator can easily be recognized by using, for example, animaging camera, and the semiconductor light-emitting element can bemounted on the projection portion by using the position of the throughhole as a reference.

In the invention of claim 9, the adhesive is transparent. If theadhesive is transparent, the color of the base board is recognizedthrough the adhesive that protrudes into the through hole. Accordingly,the color of the base board is different from the color of thesurrounding part of the through hole of the insulator. Thus, theposition of the through hole can easily be recognized on the basis ofthe boundary between the insulator and the adhesive that protrudes intothe through hole. Therefore, when the semiconductor light-emittingelement is mounted on the projection portion that penetrates the throughhole, the reference for determining the position of the semiconductorlight-emitting element, relative to the projection portion, can surelybe obtained.

The invention of claim 10 further includes a resist layer which isstacked on the insulator and the conductor. The resist layer has aplurality of openings in which the semiconductor light-emitting elementsand connection parts between the connection members and the conductorare located, and the sealing member individually covers the openings.

The resist layer may be formed of a transparent or a colored syntheticresin. In particular, it is preferable to use a white synthetic resinhaving a light reflectance of 80% or more. The white resist layer canreflect the light, which is emitted from the semiconductorlight-emitting element, in the light-extraction direction opposite tothe base board, and, advantageously, the light can efficiently beextracted. Although it is preferable that the shape of the opening ofthe resist layer be circular, this opening may have an angular shape.

In the invention of claim 10, the amount of the sealing member that isused can be reduced, compared to the case in which the sealing member isfilled so as to continuously cover all the semiconductor light-emittingelements and conductor. Moreover, in the case where the sealing memberis formed by dispensing the non-solidified resin in the opening, theflow of the non-solidified resin can be stemmed by the opening edge ofthe opening until the non-solidified resin is solidified. Thus, thenon-solidified resin can be prevented from spreading over the surface ofthe resist layer, and the height of rising of the sealing member canproperly be determined.

The invention of claim 11 further includes a frame member whichsurrounds the semiconductor light-emitting elements, and an adhesivewhich is interposed between the frame member and the insulator. Theadhesive contains a thermosetting adhesive resin and the adhesive bondsthe frame member to the insulator. The sealing member is filled in aregion which is surrounded by the frame member.

Preferably, the inner surface of the frame member should be formed as alight reflective surface. The frame member, whose inner surface is thelight reflective surface, serves also as a reflector which reflectslight that is emitted from the semiconductor light-emitting elements.The light reflective surface can be obtained by stacking a lightreflective layer on the inner surface of the frame member, or by formingthe frame member itself in white. The light reflective layer can beformed by evaporation-depositing or plating a metal with a high lightreflectance, such as aluminum or nickel, on the inner surface of theframe member, or by coating a white paint on the inner surface of theframe member. In order to form the frame member itself in white, forexample, white powder may be mixed in the resin, of which the framemember is to be formed. An example of white powder, which is usable, isa white filler such as aluminum oxide, titanium oxide, magnesium oxideor barium sulfate.

For example, a light-transmissive resin, such as transparent epoxy resinor transparent silicone resin, is usable as the sealing member. Aphosphor, which wavelength-convert light that is emitted from thesemiconductor light-emitting element to light of a different color, maybe mixed in this resin.

In the invention of claim 11, the adhesive is heated in the state inwhich the adhesive is pressed between the insulator of the base boardand the frame member. Thus, the adhesive resin, which is filled betweenthe insulator and the frame member, is solidified. Thereby, the framemember is fixed to the insulator via the adhesive.

According to the invention of claim 11, the sealing member is filled inthe region surrounded by the frame member. Thereby, all thesemiconductor light-emitting elements, which are disposed on the baseboard, can be sealed at a time. Moreover, since the adhesive containsthe adhesive resin, a work of coating an adhesive on the frame member isneedless, and there is no need to manage the amount of coating of theadhesive.

In the invention of claim 12, the conductor includes a plurality ofterminal portions which are arranged at intervals. Each of the terminalportions includes a land part for power supply and a connection partwhich connects the land part and the conductor, and the connection parthas a smaller width than the land part. The frame member crosses overthe connection parts of the terminal portions.

A power cable is connected to the land part of each terminal portion bymeans of, e.g. soldering. Thus, in order to secure the reliability ofsoldering, the width of the land part should preferably be set at, e.g.1.0 mm or more. The connection part of the terminal portion is integralwith the land part, and includes an extension part that protrudes intothe inside of the frame member. The width of the extension part may beequal to, or different from, the width of the connection part. Further,the position of connection of the connection part to the land part maybe a central area in the width direction of the land part, or may be anend area of the land part which deviates from the center of the landpart.

According to the invention of claim 12, the width of the connection partof the terminal portion, over which the frame member crosses, is smallerthan the width of the land part. Thereby, the interval between theneighboring connection parts can be increased. As a result, when theadhesive is pressed between the base board and the frame member, theadhesive deforms and easily enters between the neighboring connectionparts.

In the invention of claim 13, the width of the connection part is in arange of between 0.1 mm to less than 1.0 mm, and an interval between theneighboring connection parts is 0.2 mm or more. By this setting, theadhesive can easily enter between the neighboring connection parts, andthe adhesive can surely be filled between the connection parts.

In the invention of claim 14, the thickness of the conductor is 20 μm orless. By this setting, the surface of the insulator including theconductor is flat with little roughness. Accordingly, the adhesive caneasily come in close contact with the surface of the insulator, and theadhesive can easily enter every part and corner between the neighboringconnection parts.

According to the invention of claim 15, the adhesive resin includesprotrusion portions protruding inside the frame member. The protrusionportions cover corner parts defined by the insulator and portions of theframe member crossing over the connection parts, and the sealing membercovers the protrusion portions.

According to this structure, minute gaps, which communicate the insideand outside of the frame member, are prevented from occurring at thecorner parts. In addition, even if minute gaps occur at the cornerparts, the gaps can be sealed with the adhesive and prevented fromcommunicating with the inside of the frame member.

In the invention of claim 16, the sealing member includes a plurality oflight emission sections and grooves located between the light emissionsections. The grooves divide the neighboring light emission sections andabsorb expansion/contraction force due to the thermal expansion orthermal contraction of the sealing member. Hence, even when the sealingmember receives the heat of the semiconductor light-emitting elementsand expands/contracts, the expansion/contraction of the sealing memberis hardly transmitted to the base board. In addition, theexpansion/contraction force, which occurs in each light emissionsection, hardly affects the neighboring light emission sections, anddoes not increase the warp or distortion of other light emissionsections. Therefore, non-uniformity in color between the light emissionsections can be reduced and suppressed.

In the invention of claim 17, each of the grooves includes a bottom partwhich connects the neighboring light emission sections. The bottom partof the groove prevents deformation of the sealing member due toblow-hole.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a partly cut-out plan view showing an illumination deviceaccording to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view of the illumination device according tothe first embodiment of the invention, showing a positional relationshipbetween a semiconductor light-emitting element which is bonded to adistal end face of a projection portion, an insulator, a conductor and asealing member;

FIG. 3 is a plan view showing the positional relationship between thesemiconductor light-emitting element which is bonded to the distal endface of the projection portion, the insulator and the conductor in thefirst embodiment of the invention;

FIG. 4 is a characteristic graph showing the relationship between areflectance immediately under the semiconductor light-emitting elementand a luminous flux in the first embodiment of the invention;

FIG. 5 is a characteristic graph showing the relationship between areflectance at the periphery of the semiconductor light-emitting elementand a luminous flux in the first embodiment of the invention;

FIG. 6 is a cross-sectional view of an illumination device according toa second embodiment of the invention;

FIG. 7 is a cross-sectional view of an illumination device according toa third embodiment of the invention;

FIG. 8 is a plan view of an illumination device according to a fourthembodiment of the invention;

FIG. 9 is a plan view showing a positional relationship between asemiconductor light-emitting element which is bonded to a distal endface of a projection portion, an insulator, a conductor and a resistlayer in the fourth embodiment of the invention;

FIG. 10 is a cross-sectional view taken along line F10-F10 in FIG. 9;

FIG. 11 is a cross-sectional view taken along line F11-F11 in FIG. 9;

FIG. 12 is a cross-sectional view of an illumination device according toa fifth embodiment of the invention;

FIG. 13 is a plan view showing a positional relationship between asemiconductor light-emitting element which is bonded to a distal endface of a projection portion, an insulator, a conductor and a lightreflective layer in the fifth embodiment of the invention;

FIG. 14 is a cross-sectional view of an illumination device according toa sixth embodiment of the invention;

FIG. 15 is a plan view of an illumination device according to a seventhembodiment of the invention;

FIG. 16 is a cross-sectional view taken along line F16-F16 in FIG. 15;

FIG. 17 is a cross-sectional view taken along line F17-F17 in FIG. 14;

FIG. 18 is a plan view of an illumination device according to an eighthembodiment of the invention; and

FIG. 19 is a cross-sectional view taken along line F19-F19 in FIG. 18.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of the present invention will now be described withreference to FIG. 1 to FIG. 5.

FIG. 1 discloses an illumination device 1 which constitutes, forexample, an LED package. The illumination device 1 includes a base board2, an insulator 3, a conductor 4, a plurality of semiconductorlight-emitting elements 5, a reflector 6 and a sealing member 7.

The base board 2 has, for example, a rectangular shape in order toobtain a light emission area that is required by the illumination device1. The material of the base board 2 should preferably be a metal withgood heat radiation properties, such as copper or an aluminum alloy. Asshown in FIG. 2, the base board 2 has a front surface 2 a and a backsurface 2 b which is located opposite to the front surface 2 a. Aplurality of columnar projection portions 8 are integrally formed on thefront surface 2 a of the base board 2. The number of projection portions8 corresponds to the number of semiconductor light-emitting elements 5.

The thickness A of that part of the base board 2, which excludes theprojection portions 8, is, e.g. 0.25 mm. The back surface 2 b of thebase board 2 is used as a heat radiation surface, or a heat conductionsurface which is thermally connected to a heat sink.

As shown in FIG. 2, the projection portion 8 has a flat distal end face8 a. The distal end face 8 a of the projection portion 8 is parallel tothe front surface 2 a of the base board 2. The projection portion 8 isformed to be thicker at a proximal portion 8 b thereof, which iscontinuous with the front surface 2 a of the base board 2, than at thedistal end face 8 a thereof. In the present embodiment, the projectionportion 8 is formed to become gradually thicker from the distal end face8 a toward the proximal portion 8 b. In other words, the cross-sectionalarea of the projection portion 8 a in its diametrical directionincreases continuously from the distal end face 8 a toward the proximalportion 8 b. Accordingly, the projection portion 8 has a tapered outerperipheral surface 8 c which flares from the distal end face 8 a towardthe proximal portion 8 b. The outer peripheral surface 8 c of theprojection portion 8 is continuous with the front surface 2 a of thebase board 2, describing a gentle arcuate curve. According to thepresent embodiment, the diameter of the distal end face 8 a is, e.g.0.57 mm, and the diameter of the proximal portion 8 b is, e.g. 1.08 mm.

A light reflective layer 10 is stacked on the distal end face 8 a of theprojection portion 8. The light reflective layer 10 is formed of a thinfilm of, e.g. silver, and the thickness B thereof is 0.003 mm to 0.005mm. The light reflectance of the light reflective layer 10 is 90% ormore.

A white glass epoxy base plate, for instance, is used as the insulator 3in order to obtain a light reflecting performance. The thickness C ofthe insulator 3 may be 0.060 mm at minimum, and is, e.g. 0.25 mm in thisembodiment. As shown in FIG. 1 and FIG. 3, the insulator 3 includes aplurality of through holes 11, through which the projection portions 8penetrate. The through hole 11 has a circular shape, for instance, andits diameter is greater than the diameter of the proximal portion 8 bthat is the thickest part of the projection portion 8. The number ofthrough holes 11 agrees with the number of projection portions 8.

The insulator 3 is not limited to a single layer, and may formed of twolayers. In the case where the insulator 3 is formed of two layers, it ispossible that two glass epoxy base plates each having a thickness of0.030 mm can be stacked. The two-layer insulator 3 can have a moredielectric strength than the single-layer insulator 3.

The insulator 3 is attached to the front surface 2 a of the base board 2via an adhesive layer 12. The adhesive layer 12 is formed byimpregnating a sheet of fibrous material, such as paper or cloth, with athermosetting resin adhesive, and has electrical insulating properties.The adhesive layer 12 is interposed between the insulator 3 and the baseboard 2 and has a plurality of holes, through which the projectionportions 8 penetrate. The diameter of each hole is greater than thediameter of the proximal portion 8 b of the projection portion 8. Thethickness of the adhesive layer 12 should preferably be, e.g. 0.005 mmor less.

In the state in which the insulator 3 is attached to the front surface 2a of the base board 2, the projection portions 8 of the base board 2coaxially penetrate the through holes 11 of the insulator 3. In otherwords, the insulator 3 is stacked on that area of the front surface 2 aof the base board 2, which excludes the projection portions 8. Thereby,the projection portions 8 are exposed to the outside of the insulator 3through the through holes 11.

Since each of the through hole 11 of the insulator 3 has a greaterdiameter than the proximal portion 8 b of the projection portion 8, theinsulator 3 can be prevented from interfering with the projectionportions 8 when the insulator 3 is stacked on the front surface 2 a ofthe base board 2. Thus, the insulator 3 does not lift from the frontsurface 2 a of the base board 2. Therefore, the insulator 3 properlyoverlaps the front surface 2 a, and the position of the insulator 3,relative to the base board 2, is fixed. In other words, by overlappingthe insulator 3 on the front surface 2 a of the base board 2 so as toprevent interference between the through holes 11 of the insulator 3 andthe projection portions 8, the insulator 3 can be stacked at a properposition on the front surface 2 a.

When the insulator 3 is attached to the base board 2 by using theadhesive layer 12, the insulator 3 is pressed toward the base board 2.Thereby, the adhesive layer 12 is clamped between the base board 2 andthe insulator 3, and an excess portion of the adhesive is pushed outinto the inside of the through hole 11. More exactly, an excess portion12 a of the adhesive is pushed out and stays in an annular gap g betweenthe outer peripheral surface 8 c of the projection portion 8 and thethrough hole 11. The excess portion 12 a of the adhesive hardens in thestate in which the excess portion 12 a spreads between the outerperipheral surface 8 c of the projection portion 8 and the insulator 3.

Thereby, the insulator 3 is also attached to the projection portions 8,and the strength of adhesion of the insulator 3 to the base board 2 isincreased. Moreover, the excess portion 12 a of the adhesive functionsas an insulator having a volume resistivity of 10⁻² to 10⁻¹⁵Ω·m. As aresult, the withstand voltage between the insulator 3 and the outerperipheral surface 8 c of the projection portion 8 is improved.

The conductor 4 is an electrical conduction element for electricallyconnecting a plurality of semiconductor light-emitting elements 5. Theconductor 4 is formed of a copper foil, and is formed, by etching, onthat surface of the insulator 3, which is opposed to the base board 2,before stacking the insulator 3 on the base board 2.

As shown in FIG. 1, the conductor 4 includes a first conductor string 13and a second conductor string 14. The first and second conductor strings13 and 14 extend in the longitudinal direction of the base board 2 andare juxtaposed in parallel with a distance therebetween.

The first conductor string 13 includes a plurality of conductor portions15 and a first terminal portion 16 a. Similarly, the second conductorstring 14 includes a plurality of conductor portions 15 and a secondterminal portion 16 b. The conductor portions 15 are arranged in line atintervals in the longitudinal direction of the base board 2. In thepresent embodiment, the conductor portions 15 and the through holes 11of the insulator 3 are alternately arranged with a pitch of, e.g. 4 mm.In other words, the through hole 11, in which the projection portion 8is passed, is positioned between neighboring conductor portions 15.

The first terminal portion 16 a is formed integral with the conductorportion 15 which is located at one end of the first conductor string 13.The second terminal portion 16 b is formed integral with the conductorportion 15 which is located at one end of the second conductor string14. Power cables are electrically connected to the first and secondterminal portions 16 a and 16 b by means of, e.g. soldering.

As shown in FIG. 2, each conductor portion 15 is covered with a lightreflective layer 18. The light reflective layer 18 is formed of a silverthin film having a reflectance of 90% or more, and the thickness of thelight reflective layer 18 is 0.003 mm to 0.005 mm. The thickness D ofthe conductor portion 15 including the light reflective layer 18 is0.012 mm to 0.018 mm. The light reflective layer 18 of each conductorportion 15 and the light reflective layer 10 of each projection portion8 can be formed at the same time by, for example, electroless plating.Each of the projection portion 8 and conductor portion 15 is formed ofcopper. Thus, without putting the projection portion 8 and conductorportion 15 in a plating bath, the light reflective layer 10 can beformed on the projection portion 8, and the light reflective layer 18can be formed on the conductor portion 15. Furthermore, a resist filmmay be stacked on the light reflective layer 18.

As shown in FIG. 2 and FIG. 3, an end edge 15 a of each conductorportion 15 is spaced apart by a predetermined distance from the openingedge of the through hole 11. Thereby, a portion 3 a of the whiteinsulator 3 is exposed from between the end edge 15 a of each conductorportion 15 and the opening edge of the through hole 11. As a result, adistance for insulation, which is greater than the gap g between theouter peripheral surface 8 c of the projection portion 8 and the throughhole 11, can be secured between the end edge 15 a of each conductorportion 15 and the outer peripheral surface 8 c of the projectionportion 8. In addition, since the portion 3 a of the insulator 3 isexposed from between the end edge 15 a of each conductor portion 15 andthe opening edge of the through hole 11, light which is incident on thepart 3 a of the insulator 3 can be reflected in a light-extractiondirection opposite to the base board 2. Exactly speaking, the end edge15 a of the conductor portion 15 refers to an end edge of the lightreflective layer 18 that covers the conductor portion 15.

A double-wire type blue LED chip which uses, e.g. a nitridesemiconductor, is used as each semiconductor light-emitting element 5.The semiconductor light-emitting element 5 includes a light-transmissivesubstrate 20 and a light-emitting layer 21. A sapphire substrate, forinstance, is used as the substrate 20. The substrate 20 has a firstsurface 20 a and a second surface 20 b which is located on a sideopposite to the first surface 20 a. The semiconductor light-emittinglayer 21 is formed by successively stacking, on the first surface 20 aof the substrate 20, a buffer layer, an n-type semiconductor layer, alight emission layer, a p-type clad layer and a p-type semiconductorlayer. The light emission layer has such a quantum well structure thatbarrier layers and well layers are alternately arranged. The n-typesemiconductor layer includes an n-side electrode 22. The p-typesemiconductor layer includes a p-side electrode 23. Besides, thesemiconductor light-emitting layer 21 has no reflective film, and lightcan be emitted in both directions along the thickness thereof.

As shown in FIG. 2, the semiconductor light-emitting elements 5 aremounted on the distal end faces 8 a of the projection portions 8 thatproject from the base board 2. Specifically, the second surface 20 b ofthe substrate 20 of each semiconductor light-emitting element 5 isadhered to the distal end face 8 a of the projection portion 8 via abonding material 24. Accordingly, the semiconductor light-emittingelements 5 and the conductor portions 15 are alternately arranged with apitch of, e.g. 4 mm.

A silicone resin adhesive with light transmissivity should preferably beused as the bonding material 24. The bonding material 24 constitutes athermal resistance member which hinders heat conduction from thesemiconductor light-emitting element 5 to the projection portion 8.However, the thermal resistance of the bonding material 24 can be madesubstantially ignorable by reducing the thickness E of the bondingmaterial 24 to, e.g. 0.10 mm or less. It is desirable, therefore, tomake the thickness E of the bonding material 24 as small as possiblewithin such a range that the inherent adhesion performance of thebonding material would not be lost.

The height of the projection portion 8 including the light reflectivelayer 10 may be less than the height of the insulator 3 if thelight-emitting layer 21 of the semiconductor light-emitting element 5projects above the semiconductor portion 15 on the insulator 3, as shownin FIG. 2. However, it is preferable to set the height of the projectionportion 8 to be equal to or greater than the height of the insulator 3.In the present embodiment, the height of the projection portion 8 isdetermined such that the light reflective layer 10 is positioned higherthan the light reflective layer 18 that covers the conductor portion 15.

The dielectric strength between the semiconductor light-emitting layer21 of the semiconductor light-emitting element 5 and the projectionportion 8 can be secured by the bonding material 24 and the sapphiresubstrate 20 that is much thicker than the bonding material 24. Thethickness of the semiconductor light-emitting element 5 including thebonding material 24 is, e.g. 0.09 mm. With the use of this semiconductorlight-emitting element 5, the semiconductor light-emitting layer 21projects to a position higher than the light reflective layer 18 thatcovers the conductor portion 15. In this embodiment, the entirety of thesemiconductor light-emitting element 5 projects to a position higherthan the light reflective layer 18.

If the semiconductor light-emitting element 5 projects to a positionhigher than the light reflective layer 18, the light, which is emittedfrom the semiconductor light-emitting element 5 to the peripherythereof, can easily reach the surrounding of the through hole 11,without being blocked by the insulator 3. As a result, the light can bereflected by the surrounding of the semiconductor light-emitting element5 and can efficiently be extracted to the side opposite to the baseboard 2.

As shown in FIG. 2 and FIG. 3, each semiconductor light-emitting element5 is electrically connected to the conductor portions 15 of theconductor 4 by wire bonding. Specifically, the n-side electrode 22 ofeach semiconductor light-emitting element 5 is electrically connected aneighboring conductor portion 15 via a bonding wire 25. The p-sideelectrode 23 of the semiconductor light-emitting element 5 iselectrically connected another neighboring conductor portion 15 via abonding wire 25. The bonding wire 25 is an example of a connectionmember.

That one of the conductor portions 15 of the first conductor string 13,which is located on the side opposite to the first terminal portion 16a, and that one of the conductor portions 15 of the second conductorstring 14, which is located on the side opposite to the second terminalportion 16 b, are electrically connected via another bonding wire 26(see FIG. 1). Thus, the plural semiconductor light-emitting elements 5are connected in series on the base board 2.

When the semiconductor light-emitting element 5 is wire-bonded to theconductor portions 15, one end of the bonding wire 25 is bonded to theelectrode 22, 23 by ball bonding. Thereafter, the bonding wire 25 is ledto the conductor portion 15 by using a bonding tool, and is bonded tothe conductor portion 15. In the present embodiment, since thesemiconductor light-emitting element 5 projects to a position higherthan the conductor portion 15, the insulator 3 does not hinder themovement of the bonding wire 25 when the bonding wire 25 is moved byusing the bonding tool. Moreover, there is no need to forcibly stretchthe bonding wire 25 in an obliquely downward direction, and the wirebonding is facilitated.

When the semiconductor light-emitting element 5 is wire-bonded to theconductor portion 15, a bonding machine is made to recognize a boundarybetween the end edge 15 a of the conductor portion 15 and the insulator3, and the bonding wire 25 is bonded to that part of the conductorportion 15, which is apart from this boundary, or a reference position,by a predetermined distance G. In the present embodiment, in order tominimize a stress remaining at the bonding part of the bonding wire 25,each of a distance H1 between the end edge 15 a of the conductor portion15 and the n-side electrode 22 of the semiconductor light-emittingelement 5 and a distance H2 between the end edge 15 a of the conductorportion 15 and the p-side electrode 23 is set at, e.g. 0.25 mm to 6.0mm.

As shown in FIG. 1, the reflector 6 is formed, for example, in arectangular frame shape and surrounds all semiconductor light-emittingelements 5 on the base board 2 as a group. In other words, the reflector6 is not associated with the individual semiconductor light-emittingelements 5, but is configured as a structural element which is common toall semiconductor light-emitting elements 5.

The reflector 6 is attached to the insulator 3. In the presentembodiment, all the conductor portions 15 of the conductor 4 are locatedwithin the region surrounded by the reflector 6. The first and secondterminal portions 16 a and 16 b of the conductor 4 are located outsidethe reflector 6.

The reflector 6 is formed of, e.g. a synthetic resin, and its innerperipheral surface is formed as a light reflective surface 6 a. In thisembodiment, in order to obtain the light reflective surface 6 a, whitepowder is mixed in the resin material, of which the reflector 6 is to beformed, and thereby the light-reflective surface 6 a itself is formed ina white color with high reflectance of visible light. The reflector 6 isusable, for example, as an attachment part of a lens for controllingdistribution of light.

As shown in FIG. 2, the sealing member 7 is filled in the regionsurrounded by the reflector 6. The sealing member 7 is solidified, forexample, by heating treatment, and covers the semiconductorlight-emitting elements 5, insulator 3 and bonding wires 25 and 26 whichare located inside the reflector 6. Further, the sealing member 7 iscontinuously filled in the gap g between the through hole 11 of theinsulator 3 and the outer peripheral surface 8 c of the projectionportion 8. The sealing member 7 thus covers the excess portion 12 a ofthe adhesive, which protrudes into the through hole 11 and the outerperipheral surface 8 c of the projection 8.

The sealing member 7 is formed of a light-transmissive material such asa transparent silicone resin. A phosphor is mixed, where necessary, inthe sealing member 7. In the present embodiment, use is made of thephosphor which wavelength-convert blue primary light that is emittedfrom the blue LED chip to yellow secondary light having a differentwavelength. The phosphor is mixed, as a preferable example, in thesealing member 7 in a substantially uniformly dispersed state.

The phosphor, which is excited by blue light emitted from thesemiconductor light-emitting layer 21, absorb the blue light and emityellow light. The yellow light travels through the sealing member 7. Onthe other hand, part of the blue light emitted from the semiconductorlight-emitting layer 21 passes through the sealing member 7 withoutstriking the phosphor. By the mixing of the two complementary colors,white light can be obtained.

In addition, since the reflector 6 is formed in such a frame shape as tosurround all semiconductor light-emitting elements 5 as a group, most ofthe light, which is extracted to the outside of the illumination device1 through the sealing member 7, travels through the sealing member 7without being reflected by the light reflective surface 6 a of thereflector 6. Therefore, the loss of light due to reflection decreases,and the light emitted from the semiconductor light-emitting elements 5can efficiently be taken out of the illumination device 1.

In the illumination device 1 of the first embodiment, the excess portion12 a of the adhesive, which forms the adhesive layer 12, protrudes intothe through hole 11 of the insulator 3. Thus, the adhesive layer 12 isentirely filled between the base board 2 and the insulator 3. Therefore,no gap, which is continuous with the through hole 11, is formed betweenthe base board 2 and the insulator 3.

In the case where a gap, which is continuous with the through hole 11,is present between the base board 2 and the insulator 3, the airremaining in the gap becomes bubbles when the sealing member 7 isheated, and the bubbles flow into the sealing member 7. The air stays inthe sealing member 7 as bubbles. If moisture from the outside enters thebubbles staying in the sealing member 7, it is undeniable that thedielectric strength of the sealing member 7 lowers. According to thefirst embodiment, however, no gap, which leads to occurrence of bubbles,is formed between the base board 2 and the insulator 3. Therefore, thedecrease in the dielectric strength of the sealing member 7 can beprevented.

According to the first embodiment, the plural semiconductorlight-emitting elements 5 disposed on the base board 2 are caused toemit light, and the light is extracted to the side opposite to the baseboard 2, as shown by an arrow in FIG. 2, thus effecting illumination.Thereby, the illumination device 1 which is capable of performing arealight emission can be obtained.

In the first embodiment, the insulator 3, which effects electricalinsulation between the conductor portion 15 of the conductor 4 and thebase board 2, is excluded from between the semiconductor light-emittingelement 5 and the distal end face 8 a of the projection portion 8, andthe substrate 20 of the semiconductor light-emitting element 5 is bondedto the light reflective layer 10 of the projection portion 8.

Thus, the heat produced by the semiconductor light-emitting element 5 isdirectly conducted to the base board 2, without interference by theinsulator 3. To be more specific, the heat of the semiconductorlight-emitting element 5 is conducted to the projection portion 8 of thebase board 2 via the light reflective layer 10 of the silver thin filmfrom the bonding material 24 that is so thin that its thermal resistanceis substantially ignorable. Furthermore, since the projection portion 8is so formed as to have a gradually increasing thickness from the distalend face 8 a toward the proximal portion 8 b and the cross-sectionalarea of the projection portion 8 gradually increases toward the frontsurface 2 a of the base board 2, the heat of the semiconductorlight-emitting element 5 can efficiently be conducted from the distalend face 8 a of the projection portion 8 to the base board 2. The heatthat is conducted to the base board 2 is radiated from the back surface2 b of the base board 2 to the outside of the base board 2.

Therefore, the temperature rise of the semiconductor light-emittingelement 5 can surely be prevented, and the operation temperature of thesemiconductor light-emitting element 5 can be kept at proper values. Asa result, the decrease in light emission efficiency of the semiconductorlight-emitting element 5 can be suppressed, and the variance in lightemission amount of the semiconductor light-emitting element 5 can beeliminated. Therefore, the non-uniformity in color of light emitted fromthe respective semiconductor light-emitting elements 5 can besuppressed.

The direction of light emission is not restricted in the semiconductorlight-emitting element 5. In particular, the intensity of light emittedtoward the base board 2 is higher than the intensity of light emitted inthe light-extraction direction opposite to the base board 2. Most of thelight emitted toward the base board 2 is incident on the lightreflective layer 10 having a reflectance of 90% or more through thebonding material 24, and the light is then reflected by this lightreflective layer 10 in the light-extraction direction. In this manner,the light, which is emitted from the semiconductor light-emittingelement 5 toward the base board 2, is efficiently reflected just underthe semiconductor light-emitting element 5. Therefore, the light canefficiently be extracted.

FIG. 4 shows the relationship between the reflectance immediately underthe semiconductor light-emitting element 5 and a luminous flux. As isclearly understood from FIG. 4, as regards light with a wavelength of460 nm, the intensity of extracted light (relative intensity of emissionlight) becomes higher as the reflectance is higher. It was confirmedthat the reflectance immediately under the semiconductor light-emittingelement 5 reaches 91.35%.

Moreover, part of the light emitted from the semiconductorlight-emitting element 5 toward the base board 2 and part of the lightemitted from the phosphor within the sealing member 7 are incident onthe white insulator 3 and are reflected by the white insulator 3 in thelight-extraction direction. In addition, the part of the light emittedtoward the base board 2 is incident on the light reflective layer 18covering the conductor portion 15, and is reflected by the lightreflective layer 18 in the light-extraction direction. Besides, theportion 3 a of the insulator 3 is not covered with the conductor portion15 and is exposed to the periphery of the through hole 11. In otherwords, the portion 3 a of the insulator 3 can be regarded as a whitereflection surface which is continuous in the circumferential directionof the through hole 11. Thus, the light, which is incident on theportion 3 a of the insulator 3, can be reflected in the light-extractiondirection.

FIG. 5 shows the relationship between a mean reflectance at theperiphery of the semiconductor light-emitting element 5 and a luminousflux. As is clearly understood from FIG. 5, the intensity of extractedlight (relative intensity of emission light) becomes higher as the meanreflectance of light with a wavelength of 400 nm to 740 nm is higher. Itwas confirmed that the mean reflectance at the periphery of thesemiconductor light-emitting element 5 reaches 93.7%.

As is clear from FIG. 4 and FIG. 5, the emission light intensitydecreases as the reflectance becomes lower, and the emission lightintensity increases as the reflectance becomes higher. Thus, the lightemission efficiency (light extraction efficiency) of the illuminationdevice 1 can be enhanced by the high-efficiency reflectioncharacteristics of the light reflective layers 10 and 18 and theinsulator 3. According to experiments by the inventor of the presentinvention, it was confirmed that illumination can be effected with aluminous flux of 7.41 lm and a light emission efficiency of 125 lm/W inthe case where the power consumption of the illumination device 1 is0.06 W.

Therefore, according to the illumination device 1 of the firstembodiment, while the decrease in light emission efficiency due to thetemperature rise of the semiconductor light-emitting element 5 issuppressed, the light that is emitted from the semiconductorlight-emitting element 5 toward the base board 2 is reflected and lightcan efficiently be extracted.

Furthermore, according to the first embodiment, the annular gap g ispresent between the outer peripheral surface 8 c of the projectionportion 8 and the through hole 11 of the insulator 3, and a part of thesealing member 7 is filled in the gap g. Thus, part of the light emittedfrom the phosphor in the sealing member 7 is made incident on the outerperipheral surface 8 c of the projection portion 8 without being blockedby the insulator 3. The outer peripheral surface 8 c of the projectionportion 8 is inclined so as to flare from the distal end face 8 a of theprojection portion 8 toward the proximal portion 8 b. Thereby, the lightincident on the outer peripheral surface 8 c can positively be reflectedin the light-extraction direction opposite to the base board 2.Therefore, the light emitted from the semiconductor light-emittingelement 5 can efficiently be extracted by making use of the projectionportion 8 that promotes heat radiation of the semiconductorlight-emitting element 5.

Moreover, the bonding material 24, which bonds the semiconductorlight-emitting element 5 to the distal end face 8 a of the projectionportion 8, is the transparent silicone resin. There is very littlepossibility that the degradation of the silicone resin, including achange in color due to heat, progresses. As a result, the extraction oflight reflected by the light reflective layer 10 can be maintained ingood condition for a long time, without the light incident on the lightreflective layer 10 being blocked by the bonding material 24, or withoutthe extraction of the light reflected by the light reflective layer 10being hindered by the bonding material 24.

In the first embodiment, one semiconductor light-emitting element 5 isdisposed on the distal end face 8 a of one projection portion B. Thepresent invention, however, is not limited to this configuration. Forexample, a plurality of semiconductor light-emitting elements 5 may bedisposed on the distal end face 8 a of one projection portion 8. In thiscase, a plurality of semiconductor light-emitting elements 5, which emitlight of the same color, or a plurality of semiconductor light-emittingelements 5, which emit lights of different colors, may be employed. Inthe case where the semiconductor light-emitting elements 5 which emitlights of different colors are employed, three semiconductorlight-emitting elements 5 which emit lights of red, yellow and blue, forinstance, may be arrayed in line. By arraying the plural semiconductorlight-emitting elements 5 on the distal end face 8 a of one projectionportion 8, the entire luminous flux of the illumination device 1 can bemore improved.

FIG. 6 shows a second embodiment of the present invention. The secondembodiment differs from the first embodiment with respect to thestructure of the reflector 6. In the other structural aspects, thesecond embodiment is the same as the first embodiment. Thus, in thesecond embodiment, the structural parts common to those in the firstembodiment are denoted by like reference numerals, and a descriptionthereof is omitted.

As shown in FIG. 6, the reflector has a plurality of reflection holes 31(only one of them being shown) which are associated with thesemiconductor light-emitting elements 5. The semiconductorlight-emitting element 5, which is bonded to the projection portion 8 ofthe base board 2, is individually disposed in the reflection hole 31.The reflection hole 31 is a taper hole with a diameter which graduallyincreases from the base board 2 in the light-extraction direction. Thesealing member 7 is filled in each of the reflection holes 31. Thesealing member 7 is continuously filled in the gap g between the throughhole 11 of the insulator 3 and the outer peripheral surface 8 c of theprojection portion 8, and the sealing member 7 covers the excess portion12 a of the adhesive, which protrudes into the through hole 11 and theouter peripheral surface 8 c of the projection portion 8.

In this second embodiment, too, the heat of the semiconductorlight-emitting element 5 is let to escape directly to the base board 2,and the light traveling from the semiconductor light-emitting element 5toward the base board 2 is reflected, and thereby the light canefficiently be extracted.

Moreover, in the second embodiment, since the sealing member 7 is filledin each reflection hole 31, the amount of the sealing member 7 that isused can be made less than in the first embodiment. Besides, thereflector 6 can be used, for example, as an attachment part of a lensfor controlling distribution of the light that is passed through thesealing member 7 and is extracted.

FIG. 7 shows a third embodiment of the present invention.

The third embodiment differs from the first embodiment in that thereflector of the illumination device 1 is dispensed with. In the otherrespects, the structure of the illumination device 1 of the thirdembodiment is the same as in the first embodiment.

In the third embodiment, the semiconductor light-emitting element 5,which is bonded to the projection portion 8 of the base board 2, isindividually sealed by a sealing member 41. The sealing member 41 isformed by dispensing a non-solidified resin on each of the semiconductorlight-emitting element 5 from a dispenser (not shown). Thenon-solidified resin, after dispensed from the dispenser, is solidifiedin a hemispherical shape. The sealing member 41 includes a phosphor. Thephosphor is uniformly dispersed in the sealing member 41. Further, thesealing member 41 is continuously filled in the gap g between thethrough hole 11 of the insulator 3 and the outer peripheral surface 8 cof the projection portion 8, and covers the excess portion 12 a of theadhesive, which protrudes into the through hole 11 and the outerperipheral surface 8 c of the projection 8.

In the third embodiment, too, the heat of the semiconductorlight-emitting element 5 is let to escape directly to the base board 2,and the light traveling from the semiconductor light-emitting element 5toward the base board 2 is reflected, and thereby the light canefficiently be extracted.

Moreover, according to the third embodiment, since the pluralsemiconductor light-emitting elements 5 may individually be sealed bythe sealing member 41, the amount of the sealing member 41 that is usedcan be made less than in the first embodiment.

FIG. 8 to FIG. 11 show a fourth embodiment of the present invention.

The structure of the fourth embodiment is the same as that of the firstembodiment, except for the respects described below. Thus, in the fourthembodiment, the structural parts common to those in the first embodimentare denoted by like reference numerals, and a description thereof isomitted.

As shown in FIG. 8 and FIG. 10, a resist layer 51 is stacked on theconductor portions 15 which are covered with the light reflective layer18, and the insulator 3. The resist layer 51 prevents at least oxidationof both oxidation and sulfuration of the conductor portion 15. Theresist layer 51 is formed of a synthetic resin in which white powder,such as aluminum oxide powder, is mixed, and has electrical insulationproperties. The light reflectance of the resist layer 51 is 80% or more.The thickness of the resist layer 51 is, e.g. about 0.1 mm.

The resist layer 51 includes a plurality of openings 52 which correspondto the projection portions 8. The resist layer 51 includes a first stackportion 51 a which covers the conductor portions 15, and a second stackportion 51 b which covers the insulator 3. The first stack portion 51 aand second stack portion 51 b are integrally continuous with each other.As is clear from the comparison between FIG. 10 and FIG. 11, the heightof the first stack portion 51 a relative to the insulator 3 and theheight of the second stack portion 51 b relative to the insulator 3 aredifferent by a degree corresponding to the thickness of the conductorportion 15 including the light reflective layer 18.

As shown in FIG. 9, the opening 52 is circular and the diameter of theopening 52 is several times greater than the diameter of the projectionportion 8. When the resist layer 51 is viewed in plan, one projectionportion 8 is coaxially located inside each opening 52. In addition, thesemiconductor light-emitting element 5, which is bonded to the lightreflective layer 10 of the projection portion 8, and the two bondingwires 25, which are connected to the semiconductor light-emittingelement 5, are located inside each opening 52. Furthermore, theconnection parts between the two conductor portions 15, which are sodisposed as to sandwich the semiconductor light-emitting element 5, andthe bonding wires 25 are located inside each opening 52. Thus, theresist layer 51 covers the insulator 3 in such a manner as to excludethe through hole 11 through which the projection portion 8 penetrates,and the end portions of the conductor portions 15 neighboring theprojection portion 8.

As shown in FIG. 10 and FIG. 11, the openings 52 of the resist layer 51are individually sealed by the sealing member 53. The sealing member 53is formed by dispensing a non-solidified resin in each opening 52 fromthe dispenser (not shown). The non-solidified resin, after dispensedfrom the dispenser, is solidified in a hemispherical shape. The sealingmember 53 includes a phosphor. The phosphor is uniformly dispersed inthe sealing member 53.

The sealing member 53 continuously covers the semiconductorlight-emitting element 5 located within each opening 52, the two bondingwires 25 and the end portions of the conductor portions 15, to which thebonding wires 25 are connected. Moreover, the sealing member 7 iscontinuously filled in the gap g between the through hole 11 of theinsulator 3 and the outer peripheral surface 8 c of the projectionportion 8. The sealing member 7 thus covers the excess portion 12 a ofthe adhesive, which protrudes into the through hole 11 and the outerperipheral surface 8 c of the projection 8.

In this fourth embodiment, too, the heat of the semiconductorlight-emitting element 5 is let to escape directly to the base board 2,and the light traveling from the semiconductor light-emitting element 5toward the base board 2 is reflected, and thereby the light canefficiently be extracted.

Since the resist layer 51, which covers the conductor portion 15 andinsulator 3, is white, the light emitted from the semiconductorlight-emitting element 5 can be reflected by the resist layer 51 in thelight-extraction direction opposite to the base board 2. Therefore, thelight emitted from the semiconductor light-emitting element 5 canefficiently be extracted.

Besides, since the sealing member 53 individually covers the openings 52of the resist layer 51, the amount of use of the sealing member 53 inwhich the phosphor is mixed can be made less than in the firstembodiment.

Moreover, since the sealing member 53 is obtained by dispensing thenon-solidified resin in the opening 52, the flow of the non-solidifiedresin can be stemmed by the opening edge of the opening 52 until thenon-solidified resin is solidified. Thus, the non-solidified resin canbe prevented from spreading over the surface of the resist layer 51, andthe height of rising of the sealing member 53 can properly bedetermined. Therefore, a sufficient thickness of that part of thesealing member 53, which covers the semiconductor light-emitting element5, can be secured, and the semiconductor light-emitting element 5 andthe bonding wires 25 can surely be sealed by the sealing member 53.

FIG. 12 and FIG. 13 show a fifth embodiment of the present invention.

The structure of the fifth embodiment is the same as that of the firstembodiment, except for the respects described below. Thus, in the fifthembodiment, the structural parts common to those in the first embodimentare denoted by like reference numerals, and a description thereof isomitted.

In the fifth embodiment, a resin adhesive sheet is used as the adhesivelayer 12. The color of the adhesive layer 12, which is formed by usingthe resin adhesive sheet, is brown, and the light reflectance of theadhesive layer 12 is lower than that of the white insulator 3. Theadhesive layer 12 has a plurality of holes corresponding to theprojection portions 8 of the base board 2. The diameter of each hole isgreater than the diameter of the proximal portion 8 b of the projectionportion 8. The thickness I of the adhesive layer 12 is several timesgreater than the thickness of the adhesive layer 12 in the firstembodiment.

The adhesive layer 12 is laid over the front surface 2 a of the baseboard 2 in the state in which the projection portion 8 is passed throughthe associated hole. After the adhesive layer 12 is laid over the baseboard 2, the insulator 3 is laid over the adhesive layer 12. Themutually stacked base board 2, adhesive layer 12 and insulator 3 arepressed in the direction of stacking, and thereby the base board 2 andthe insulator 3 are bonded by the adhesive layer 12. As shown in FIG.12, since the adhesive layer 12 is pressed between the base board 2 andthe insulator 3, the opening edge of the hole of the adhesive layer 12protrudes into the through hole 11. Specifically, the excess portion 12a of the adhesive layer 12 is protruded into the annular gap g betweenthe outer peripheral surface 8 c of the projection portion 8 and thethrough hole 11. The excess portion 12 a is solidified in the state inwhich the excess portion 12 a is continuous in the circumferentialdirection of the through hole 11. The dimension J of protrusion of theexcess portion 12 a is, e.g. 0.2 mm or less. The dimension J ofprotrusion can be adjusted by adjusting the thickness of the adhesivelayer 12 and the pressing force on the adhesive layer 12. Moreover, theexcess portion 12 a of the adhesive layer 12 covers the front surface 2a of the base board 2 and rises in the through hole 11.

In the fifth embodiment, a side light reflective layer 61 is stacked onthe outer peripheral surface 8 c of each projection portion 8. The sidelight reflective layer 61 is continuous with the light reflective layer10 stacked on the distal end face 8 a of the projection portion 8 andwith the excess portion 12 a of the adhesive layer 12. The side lightreflective layer 61 is a silver thin film which is similar to the lightreflective layer 10, and is formed together with the light reflectivelayer 10 by electroless plating on the projection portion 8. Since theelectroless plating is performed before the insulator 3 is attached tothe base board 2, the side light reflective layer 61 is not formed onthe excess portion 12 a of the adhesive layer 12. Thus, the side lightreflective layer 61 does not reach that part of the base board 2, whichis covered with the excess portion 12 a of the adhesive layer 12.

Further, the sealing member 7 is continuously filled in the gap gbetween the through hole 11 of the insulator 3 and the outer peripheralsurface 8 c of the projection portion 8, and the sealing member 7 thuscovers the excess portion 12 a of the adhesive layer 12, which protrudesinto the through hole 11 and the outer peripheral surface 8 c of theprojection 8.

In the fifth embodiment, too, the heat of the semiconductorlight-emitting element 5 is let to escape directly to the base board 2,and the light traveling from the semiconductor light-emitting element 5toward the base board 2 is reflected, and thereby the light canefficiently be extracted.

Moreover, in the fifth embodiment, the outer peripheral surface 8 c ofthe projection portion 8 is covered with the side light reflective layer61, and the side light reflective layer 61 is continuous with the lightreflective layer 10 that covers the distal end face 8 a of theprojection portion 8. Thus, part of the light emitted from the phosphorin the sealing member 7 is incident not only on the light reflectivesurface 10 at the distal end of the projection portion 8, but also onthe side light reflective layer 61 via the gap g. Accordingly, the sidelight reflective layer 61 reflects the light, which travels toward theouter peripheral surface 8 c of the projection 8, in thelight-extraction direction opposite to the base board 2. Thereby, thelight can efficiently be extracted.

According to experiments conducted by the inventor, the entire luminousflux of the illumination device 1, in which the distal end face 8 a andouter peripheral surface 8 c of the projection 8 are covered with thelight reflective layers 10 and 18, was 110, in the case where the entireluminous flux of the illumination device, in which no light reflectivelayer is provided on the projection portion 8, was set at 100.Therefore, according to the illumination device 1 of the fifthembodiment, the light extraction efficiency can be increased by 10%.

In the fifth embodiment, the excess portion 12 a of the adhesive layer12 rises from the base board 2 between the outer peripheral surface 8 cof the projection section 8 and the through hole 11. It is henceundeniable that the area of the side light reflective layer 61 isdecreased by the excess portion 12 a. However, since the dimension J ofprotrusion of the excess portion 12 a is 0.2 mm or less and is verysmall, the decrease in area of the side light reflective layer 61 ispractically ignorable. In addition, even if the color of the adhesivelayer 12 is, for example, brown or black, other than white, the lightabsorbing function of the excess portion 12 a of the adhesive layer 12is also substantially ignorable.

In the fifth embodiment, the height of the excess portion 12 a of theadhesive layer 12, which protrudes into the through hole 11, can be madesubstantially equal to the height of the surface of the insulator 3.Even in the case where the height of the excess portion 12 a of theadhesive layer 12 is increased, the distal end face 8 a of theprojection portion 8, which is covered with the light reflective layer10, projects higher than the surface of the insulator 3. Thus, all theside light reflective layer 61 is not covered with the excess portion 12a. Therefore, even if the adhesive layer 12 is colored, the lighttraveling toward the projection portion 8 can be reflected by the sidelight reflective layer 61, and the light can efficiently be extracted.

Furthermore, if the height of the excess portion 12 a of the adhesivelayer 12 is increased and made substantially equal to the height of thesurface of the insulator 3, most of the gap g is filled with the excessportion 12 a. Thus, when a non-solidified resin is filled in the regionsurrounded by the reflector 6, air hardly remains in the through hole11. Therefore, by virtue of the presence of the adhesive layer 12, nogap occurs between the base board 2 and the insulator 3, and bubbles areprevented from remaining in the sealing member 7.

According to the fifth embodiment, since the adhesive layer 12 is brown,there is a sharp contrast between the excess portion 12 a of theadhesive layer 12, which protrudes into the through hole 11, and thewhite insulator 3. Thereby, the position of the through hole 11 of theinsulator 3 can easily be recognized. Accordingly, the semiconductorlight-emitting element 5 can be bonded to the projection portion 8 byusing the position of the through hole 11 as a reference position.

Specifically, in the case where the semiconductor light-emitting element5 is bonded to the projection portion 8 that penetrates the through hole11, a region of the through hole 11 is first imaged by a CCD camera thatis provided in a mounting device for bonding the semiconductorlight-emitting element 5 to the projection portion 8. Subsequently, theimage captured by an image recognition unit of the mounting device isrecognized, and the recognized image is collated with a reference imagethat is prestored in the image recognition unit. Thereby, when thesemiconductor light-emitting element 5 is to be bonded to the projectionportion 8, a reference position for determining the position of thesemiconductor light-emitting element 5, relative to the projectionportion 8, is set. The mounting device bonds the semiconductorlight-emitting element 5 to a position based on the reference positionthat is set.

In the fifth embodiment, the color of the excess portion 12 a of theadhesive layer 12 is brown, and the light reflectance of the excessportion 12 a is lower than that of the white insulator 3. Thus, theimage recognition unit can easily recognize the through hole 11 that islocated at the boundary between the insulator 3 and the excess portion12 a of the adhesive layer 12. As a result, when the semiconductorlight-emitting element 5 is to be bonded to the projection portion 8that penetrates the through hole 11, the reference for determining theposition of the semiconductor light-emitting element 5, relative to theprojection portion 8, can surely be acquired.

In the fifth embodiment, it is not necessary that the adhesive layer 12be colored in brown. The adhesive layer 12 may be transparent. In thecase where the excess portion 12 a of the adhesive layer 12 istransparent, the color of the image of the base board 2, which iscaptured through the excess portion 12 a, becomes the color of thematerial of the base board 2. For example, if the base board 2 is formedof copper, the color of the base board 2 is brown. If the base board 2is formed of a carbon-based material, the color of the base board 2 isblack. The brown or black base board 2 has a lower reflectance than thewhite insulator 3.

As a result, the color of the base board 2, which is recognized throughthe excess portion 12 a of the adhesive layer 12, is different from thecolor of the peripheral portion of the through hole 11 of the insulator3, and the through hole 11, which is located at the boundary between theinsulator 3 and the excess portion 12 a of the adhesive layer 12, caneasily be recognized. Hence, when the semiconductor light-emittingelement 5 is to be bonded to the projection portion 8 that penetratesthe through hole 11, the reference for determining the position of thesemiconductor light-emitting element 5, relative to the projectionportion 8, can surely be acquired.

FIG. 14 shows a sixth embodiment of the present invention.

The sixth embodiment differs from the fifth embodiment with respect tothe structure of the reflector 6. In the other respects, the structureof the illumination device 1 of the sixth embodiment is the same as thatof the illumination device 1 of the fifth embodiment. Thus, in the sixthembodiment, the structural parts common to those in the fifth embodimentare denoted by like reference numerals, and a description thereof isomitted.

As shown in FIG. 14, the reflector 6 has a plurality of reflection holes71 (only one of them being shown) which are associated with thesemiconductor light-emitting elements 5. The semiconductorlight-emitting element 5, which is bonded to the light reflective layer10 of the projection portion 8, is individually disposed in thereflection hole 71. The reflection hole 71 is a taper hole with adiameter which gradually increases from the base board 2 in thelight-extraction direction. The sealing member 7 is filled in each ofthe reflection holes 71. The sealing member 7 is continuously filled inthe gap g between the through hole 11 of the insulator 3 and the outerperipheral surface 8 c of the projection portion 8, and the sealingmember 7 covers the excess portion 12 a of the adhesive layer 12, whichprotrudes into the through hole 11 and the outer peripheral surface 8 cof the projection portion 8.

In this sixth embodiment, too, the heat of the semiconductorlight-emitting element 5 is let to escape directly to the base board 2.In addition, the light traveling from the semiconductor light-emittingelement 5 toward the base board 2 is reflected by the light reflectivelayer 10 and the side light reflective layer 61 of the projectionportion 8, and thereby the light can efficiently be extracted.

Moreover, since the sealing member 7 is filled in each reflection hole71, the amount of the sealing member 7 that is used can be made lessthan in the fifth embodiment.

FIG. 15 to FIG. 17 shows an illumination device 100 according to aseventh embodiment of the present invention. The illumination device 100includes a base board 101, a plurality of semiconductor light-emittingelements 102, a reflector 103, an adhesive member 104 and a sealingmember 105.

The base board 101 is formed in a rectangular shape in order to obtain alight emission area that is required by the illumination device 100. Thematerial of the base board 101 should preferably be a metal with goodheat radiation properties, such as copper. The base board 101 has afront surface 101 a. An insulator 106 is stacked on the front surface101 a. The insulator 106 is formed of, e.g. a white synthetic resin. Thethickness of the base board 101 including the insulator 106 is, e.g. 0.5mm.

A conductor 108 is formed on the insulator 106. The conductor 108includes a plurality of conductor strings 109. The conductor strings 109extend in the longitudinal direction of the base board 101 and aredisposed in parallel with an interval therebetween. The interval of theconductor strings 109 is, e.g. 3.0 mm.

Each of the conductor strings 109 includes a plurality of conductorportions 110 and a pair of terminal portions 111. The conductor portions110 and the terminal portions 111 are formed by stacking silver platinglayers on the copper surface. As shown in FIG. 17, the thickness t ofthe conductor portion 110 is set at 20 μm or less, preferably 14 μm. Theconductor portions 110 are arranged in line at intervals of, e.g. 3.0 mmin the longitudinal direction of the base board 101.

One of the terminal portions 111 is continuous with the conductorportion 110 that is located at one end of each conductor string 109, andis located at one end in the longitudinal direction of the base board101. The other terminal portion 111 is continuous with the conductorportion 110 that is located at the other end of each conductor string109, and is located at the other end in the longitudinal direction ofthe base board 101. Accordingly, the pair of terminal portions 111 arespaced apart in the longitudinal direction of the conductor string 109,and the terminal portions 111 are arranged at intervals of, e.g. 3.0 mmin a direction perpendicular to the longitudinal direction of the baseboard 2.

As shown in FIG. 15, each terminal portion 111 includes a land part 113and a connection part 114. The land part 113 is a part to which a powercable that is connected to an external power supply is soldered, and theland part 113 has a strip shape extending in the longitudinal directionof the base board 101. The width of the land part 113 is, e.g. 1.0 mm.

The connection part 114 is formed integral with the land part 113, andextends from the land part 113 toward the conductor portion 110. Thewidth of the connection part 114 is, e.g. 0.1 mm to less than 1.0 mm,preferably 0.5 mm, and is less than the width of the land part 113. Anend portion of the connection part 114, which is opposite to the landpart 113, functions also as a conductor portion 110 that is located atone end and the other end of the conductor string 109. Accordingly, thewidth of the connection part 114 is equal to the width of the conductorportion 110. Moreover, the interval P between the connection parts 114,which neighbor in the direction perpendicular to the longitudinaldirection of the base board 101, should preferably be 0.2 mm or more,and is 2.5 mm in the present embodiment.

Like the first embodiment, a double-wire type blue LED chip is used aseach semiconductor light-emitting element 102. As shown in FIG. 15, thesemiconductor light-emitting element 102 is bonded to the distal endface of a columnar projection portion 115 which projects from the baseboard 101. The projection portion 115 penetrates the insulator 106 andprojects above the insulator 106, and is located between neighboringconductor portions 110. Further, like the first embodiment, theprojection portion 115 is formed to become gradually thicker from thedistal end face, on which the semiconductor light-emitting element 102is bonded, toward the base board 101. Accordingly, the outer peripheralsurface of the projection portion 115 has a taper shape which flarestoward the base board 101 so as to reflect light, which is emitted fromthe semiconductor light-emitting element 102, in a direction opposite tothe base board 101.

The semiconductor light-emitting element 102 is electrically connectedto the neighboring conductor portions 110 via a pair of bonding wires116. As a result, a plurality of semiconductor light-emitting elements102 are connected in series in each of the conductor strings 109 of theconductor 108.

The reflector 103 is an example of a frame member. The reflector 103 isformed, for example, in a rectangular frame shape and surrounds allsemiconductor light-emitting elements 102 as a group. In other words,the reflector 103 is not associated with the individual semiconductorlight-emitting elements 102, but is configured as a structural elementwhich is common to all semiconductor light-emitting elements 102.

The reflector 103 is formed of, e.g. a synthetic resin, and its innerperipheral surface is formed as a light reflective surface 103 a. In thepresent embodiment, in order to obtain the light reflective surface 103a, a white filler, such as magnesium oxide, is mixed in the resin, ofwhich the reflector 103 is to be formed. The thickness of the reflector103 is, e.g. 1.0 mm.

The reflector 103 includes first to fourth edge portions 117 a, 117 b,117 c and 117 d. The first edge portion 117 a extends along onelongitudinal side edge of the base board 101. The second edge portion117 b extends along the other longitudinal side edge of the base board101. The third edge portion 117 c extends between one end of the firstedge portion 117 a and one end of the second edge portion 117 b. Thefourth edge portion 117 d extends between the other end of the firstedge portion 117 a and the other end of the second edge portion 117 b.Accordingly, the third and fourth edge portions 117 c and 117 d extendin a direction perpendicular to the longitudinal direction of the baseboard 101, and cross over the terminal portions 111 of the conductorstrings 109. To be more specific, the third and fourth edge portions 117c and 117 d of the reflector 103 cross over the connection parts 114 ofthe terminal portions 111. Thereby, all the conductor portions 110 ofthe conductor 108 are located within the region surrounded by thereflector 103, and all the land parts 113 of the conductor 108 arelocated outside the reflector 103.

As shown in FIG. 16 and FIG. 17, the adhesive member 104 bonds thereflector 103 to the insulator 106 of the base board 101. The adhesivemember 104 is formed in a rectangular shape and has a size correspondingto the reflector 103. The adhesive member 104 is formed by impregnatinga frame-shaped base with a thermosetting adhesive resin. A siliconeresin is usable as the adhesive resin. The thickness of the adhesivemember 104 is greater than that of the conductor portion 110 and is lessthan that of the reflector 103. Specifically, the thickness of theadhesive member 104 is, e.g. 0.15 mm. The width of the adhesive member104 is equal to, or slightly less than, the width of each of the firstto fourth edge portions 117 a, 117 b, 117 c and 117 d.

The adhesive member 104 is attached in advance to that surface of thereflector 103, which faces the insulator 106, and is formed integralwith the reflector 103. The reflector 103 with the adhesive member 104is placed on the base board 101 to which the semiconductorlight-emitting elements 102 are bonded, and is pressed toward the baseboard 101. In this state, the base board 101 is passed into a heatingfurnace and the adhesive member 104 is thermally cured. Thereby, thereflector 103 is attached to the insulator 106 of the base board 101.

The adhesive member 104, when heated, is clamped between the reflector103 and the insulator 106 of the base board 101 and is deformed.Thereby, part of the adhesive resin, which is contained in the base,protrudes to the inside and outside of the reflector 103. As shown inFIG. 16, protrusion portions 104 a of the adhesive resin cover at leastcorner portions which are defined by the inner surfaces of the third andfourth edge portions 117 c and 117 d of the reflector 103 and thesurface of the insulator 106. Furthermore, the protrusion portions 104 aextend continuously along the inner surfaces of the third and fourthedge portions 117 c and 117 d in the direction perpendicular to thelongitudinal direction of the base board 101. The protrusion portions104 a are naturally formed when the adhesive member 104 is pressedbetween the reflector 103 and the insulator 106. Thus, the formation ofthe protrusion portions 104 a is not time-consuming, and this isadvantageous in that the reflector 103 is easily attached.

The length K of protrusion of the protrusion portion 104 a from theinner surface of each of the third and fourth edge portions 117 c and117 d should preferably be set at 0.2 mm or less. The reason is asfollows.

For example, in the case where the adhesive resin is colored in a colorother than white, there is a concern that light emitted from thesemiconductor light-emitting element 102 is absorbed by the protrusionportion 104 a of the adhesive resin. However, since the length K ofprotrusion of the protrusion portion 104 a is 0.2 mm or less and is verysmall, the area of the protrusion portion 104 a is very small.Accordingly, the light absorption function of the protrusion portion 104a becomes ignorable, and it is possible to prevent the protrusionportion 104 a from hindering efficient extraction of light.

In addition, when wire bonding is applied to the semiconductorlight-emitting element 102 after the reflector 103 is attached to thebase board 102, interference between the bonding tool and the protrusionportion 104 a of the adhesive resin can be avoided. Thus, the bondingtool is prevented from being stained and damaged by the adhesive resin.

As shown in FIG. 16, the sealing member 105 is filled in the regionsurrounded by the reflector 103. The sealing member 105 covers all thesemiconductor light-emitting elements 102 located inside the reflector103, insulator 106 and bonding wires 116. Further, the sealing member105 covers the protrusion portion 104 a of the adhesive resin, which islocated inside the reflector 103.

The sealing member 105 is formed of, e.g. a thermosetting siliconeresin. The silicone resin is filled inside the reflector 103 and issubjected to heat treatment and solidified.

A phosphor is mixed in the silicone resin, of which the sealing member105 is formed. The phosphor is mixed, as a preferable example, in thesealing member 105 in a substantially uniformly dispersed state. In thepresent embodiment, use is made of the phosphor which wavelength-convertblue primary light that is emitted from the semiconductor light-emittingelement 102 to yellow secondary light having a different wavelength. Bythe mixing of the two complementary colors, white light emitted from theillumination device 100.

According to the seventh embodiment, the heat of the semiconductorlight-emitting element 102 can be let to escape directly to theprojection portion 115 of the base board 101, and the decrease in lightemission efficiency due to the temperature rise of the semiconductorlight-emitting element 102 can be suppressed. Besides, the lighttraveling from the semiconductor light-emitting element 102 toward thebase board 101 is reflected, and thereby the light can efficiently beextracted.

In the seventh embodiment, by filling the sealing member 105 inside thereflector 103 that is attached to the base board 101, all thesemiconductor light-emitting elements 102, which are bonded to theprojection portions 115 of the base board 101, and the bonding wires 116can be sealed by the sealing member 105 at a time.

Moreover, the adhesive member 104, which bonds the reflector 103 to theinsulator 106 of the base board 101, is formed by impregnating the basewith the adhesive resin. Thus, a work of coating an adhesive to thereflector 103 is needless, and there is no need to manage the amount ofcoating of the adhesive. Therefore, the work that is needed for thefabrication of the illumination device 100 can be simplified, and themanufacturing cost can be reduced.

According to the seventh embodiment, the width of the land part 113 ofeach terminal portion 111 of the conductor 108 is greater than the widthof the connection part 114 thereof. Thus, when a power cable is solderedto the land part 113, a sufficient contact area can be secured betweenthe land part 113 and the power cable. Therefore, the power cable can beconnected to the land part 113 in an electrically stable state.

Besides, the width of the connection part 114 of each of the terminalportions 111, over which the third and fourth edge portions 117 c and117 d of the reflector 103 cross, is less than the width of the landpart 113 of each terminal portion 111. Thereby, the pitch P betweenneighboring connection parts 114 can be increased. In other words, evenin the case where the pitch between neighboring conductor strings 109 isreduced as small as possible, the pitch P between the connection parts114 can be increased.

As a result, when the reflector 103 is pressed toward the base board101, that part of the adhesive member 104, which extends along the thirdand fourth edge portions 117 c and 117 d of the reflector 103, deformsand easily enter between the neighboring connection parts 114. In thepresent embodiment, since the interval between the neighboringconnection parts 114 is set at 2.5 mm, the adhesive member 104 moreeasily enter between the neighboring connection parts 114.

Moreover, at the initial stage of heat treatment, the adhesive member104 temporarily softens. Thereby, the adhesive member 104 easily entersevery part and corner between the neighboring connection parts 114.Besides, in the present embodiment, since the thickness of eachconductor string 109 including connection parts 114 is 14 μm and issmall, the surface of the insulator 106 including the conductor 108 isflat with little roughness. Accordingly, the adhesive member 104 caneasily come in close contact with the surface of the insulator 106, andthe adhesive member 104 can easily enter every part and corner betweenthe neighboring connection parts 114.

As a result, as shown in FIG. 17, corner parts L, which are defined bythe surface of the insulator 106 and the side surfaces of the connectionparts 114 standing on the surface of the insulator 106, can surely befilled with the adhesive member 104. Therefore, minute gaps, whichcommunicate the inside and outside of the reflector 103, are preventedfrom occurring at the corner parts L.

Besides, the adhesive member 104 covers the corner parts L. Thus, evenif minute gaps occur at the corner parts L, the gaps can be sealed withthe adhesive member 104 and prevented from communicating with the insideof the reflector 103.

Hence, when the non-solidified silicone resin, which is filled insidethe reflector 103, is subjected to heat treatment to form the sealingmember 105, the non-solidified silicone resin is prevented from leakingto the outside of the reflector 103 through the corner parts L. Thereby,no silicone resin is wasted, and the sealing member 105 can be formed ofa predetermined amount of silicone resin.

Furthermore, when the non-solidified silicone resin is heated, theadhesive 104 can shield flow of air, which remains at the corner part Land expands, to the inside of the reflector 103. Therefore, the airremaining at the corner part L is prevented from becoming bubbles andstaying in the sealing member 105, and the degradation in insulationperformance of the sealing member 105 can be prevented.

FIG. 18 and FIG. 19 show an eighth embodiment of the present invention.

The eighth embodiment differs from the seventh embodiment with respectto the structure of the sealing member 105. In the other respects, thestructure of the illumination device 100 of the eighth embodiment isbasically the same as that of the illumination device 100 of the seventhembodiment. Thus, in the eighth embodiment, the structural parts commonto those in the seventh embodiment are denoted by like referencenumerals, and a description thereof is omitted.

As shown in FIG. 18, the sealing member 105 that covers thesemiconductor light-emitting elements 102 includes a plurality of lightemission sections 200. Each light emission section 200 has a strip shapeextending in the longitudinal direction of the base board 101, and thelight emission sections 200 are arranged in the direction perpendicularto the longitudinal direction of the base board 101. Each light emissionsection 200 includes two juxtaposed strings of semiconductorlight-emitting elements 102. Hence, each light emission section 200 ismade to emit, for example, white light, by the light radiated from thetwo strings of semiconductor light-emitting elements 102.

A plurality of grooves 201 are formed in the surface of the sealingmember 105. The grooves 201 extend in the longitudinal direction of thebase board 101 and are arranged in parallel at intervals in thedirection perpendicular to the longitudinal direction of the base board101. The grooves 201 are positioned at boundaries between theneighboring light emission sections 200. A bottom part 201 a of eachgroove 201 lies between the neighboring light emission sections 200.

The heat that is produced by the semiconductor light-emitting elements102 conducts to the base board 101 which supports the semiconductorlight-emitting elements 102, and to the sealing member 105 which coversthe semiconductor light-emitting elements 102. The thermal expansioncoefficient of the sealing member 105 differs from that of the baseboard 101 due to the difference in material. In general, thermalexpansion/contraction tends to more easily occur in the sealing member105 than in the base board 101. Accordingly, if the sealing member 105expands/contracts due to the thermal effect of the semiconductorlight-emitting elements 102, this may lead to warp or distortion of thebase board 101 to which the sealing member 105 is attached.

According to the eighth embodiment, the grooves 201, which divide theneighboring light emission sections 200, are formed in the surface ofthe sealing member 105. The grooves 201 absorb expansion/contractionforce due to the thermal expansion or thermal contraction of the sealingmember 105. Hence, even when the sealing member 105 receives the heat ofthe semiconductor light-emitting elements 102 and expands/contracts, theexpansion/contraction of the sealing member 105 can be absorbed withinthe sealing member 105. Therefore, the expansion/contraction force ofthe sealing member 105 is hardly transmitted to the base board 101, andthe warp and distortion of the base board 101 can be prevented.

Moreover, the plural light emission sections 200 of the sealing member105 are divided by the grooves 201. Thus, the expansion/contractionforce, which occurs in each light emission section 200, hardly affectsthe neighboring light emission sections 200, and does not increase thewarp or distortion of other light emission sections 200. Therefore,non-uniformity in color between the light emission sections 200 can bereduced and suppressed.

The sealing member 105 may be formed by, for example, injection molding.Thereby, the non-solidified resin, of which the sealing member 105 is tobe formed, is filled in the mold, and thus the thickness of the lightemission sections 200 becomes uniform. Furthermore, since the grooves201 having bottom parts 201 a are formed between the light emissionsections 200, deformation of the sealing member 105 due to blow-hole canbe prevented.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. An illumination device comprising: a base board having heat radiationproperties, the base board including a surface and projection portionsformed to become gradually thicker from its ends toward the surface ofthe base board; an insulator formed on the surface of the base board; aconductor formed on the insulator; a plurality of semiconductorlight-emitting elements which are mounted on the projection portions ofthe base board; connection members which electrically connect theconductor and the semiconductor light-emitting elements; and alight-transmissive sealing member which covers the insulator, theprojection portions, the semiconductor light-emitting elements and theconnection members.
 2. The illumination device according to claim 1,wherein the projection portion has a distal end face, on which thesemiconductor light-emitting element is mounted, and an outer peripheralsurface which flares from the distal end face toward the surface of thebase board.
 3. The illumination device according to claim 2, wherein theinsulator has a plurality of through holes through which the projectionportions penetrate, and each of the through holes has a greater diameterthan the projection portion.
 4. The illumination device according toclaim 3, further comprising an adhesive bonding the insulator to thesurface of the base board, and a part of the adhesive protruding to aninside of the through hole.
 5. The illumination device according toclaim 4, wherein a light reflective layer is formed on the distal endface of each projection portion, and the semiconductor light-emittingelement is bonded to the light reflective layer by a light-transmissivebonding material.
 6. The illumination device according to claim 5,wherein a side light reflective layer is formed on the outer peripheralsurface of each projection portion, the side light reflective layer iscontinuous with the light reflective layer and with a part of theadhesive that protrudes into the through hole, and the sealing memberincludes a phosphor excited by a light emitted from the semiconductorlight-emitting elements.
 7. The illumination device according to claim6, wherein a dimension of protrusion of the adhesive into the throughhole is 0.2 mm or less.
 8. The illumination device according to claim 4,wherein a light reflectance of the insulator is different from a lightreflectance of the adhesive.
 9. The illumination device according toclaim 8, wherein the adhesive is transparent.
 10. The illuminationdevice according to claim 1, further comprising a resist layer, stackedon the insulator and the conductor, and having a plurality of openingsin which the semiconductor light-emitting elements and connection partsbetween the connection members and the conductor are located, and thesealing member individually sealing the openings.
 11. The illuminationdevice according to claim 1, further comprising: a frame member whichsurrounds the semiconductor light-emitting elements; and an adhesivewhich contains a thermosetting adhesive resin and is interposed betweenthe frame member and the insulator, the adhesive bonding the framemember to the insulator, and the sealing member being filled in a regionwhich is surrounded by the frame member.
 12. The illumination deviceaccording to claim 11, wherein the conductor includes a plurality ofterminal portions arranged at intervals, each of the terminal portionsincludes a land part for power supply and a connection part connectingthe land part and the conductor, the connection part has a smaller widththan the land part, and the frame member crosses over the connectionparts of the terminal portions.
 13. The illumination device according toclaim 12, wherein a width of the connection part is in a range ofbetween 0.1 mm to less than 1.0 mm, and an interval between neighboringsaid connection parts is 0.2 mm or more.
 14. The illumination deviceaccording to claim 12, wherein a thickness of the conductor is 20 μm orless.
 15. The illumination device according to claim 12, wherein theadhesive resin includes protrusion portions protruding inside the framemember, the protrusion portions cover corner parts defined by theinsulator and portions of the frame member crossing over the connectionparts, and the sealing member covers the protrusion portions.
 16. Theillumination device according to claim 1, wherein the sealing memberincludes grooves located between light emission sections.
 17. Theillumination device according to claim 16, wherein each of the groovesincludes a bottom part which connects neighboring the light emissionsections.